Emotional events are memorable. If I talk to people from my parent’s generation, they can all tell you where they were and what they were doing when they heard that President Kennedy had been shot, even though this happened almost 50 years ago. For my generation, the day of the explosion of the space shuttle Challenger as well as the attacks on 9/11 have the same force and vividness in memory.

All of this would make it seem as though negative events are particularly memorable. And, of course, there is some reason to want to remember negative things that happened in detail. In the 1970s, motivated by people’s memories of the Kennedy assassination, Roger Brown and James Kulik suggested that it was valuable to remember surprising negative events because that information would be useful for planning in the future.